This invention relates to transmission systems in downhole components, more specifically to transmission systems comprising inductive couplers. U.S. Pat. No. 6,670,880, which is incorporated herein by reference, discloses a downhole transmission system through a string of downhole components. A first transmission element is located in one end of each downhole component, which includes a first magnetically-conductive, electrically-insulating (MCEI) trough, and a first electrically conductive coil lying there in. A second data transmission element is located in the other end, with a similar arrangement comprising a second magnetically-conductive, electrically-insulating trough and a second electrically conductive coil. The transmission system further comprises an electrical conductor in electrical communication with and running between each first and second coil in the downhole component. The string of downhole components is cooperatively arranged such that the troughs are in magnetic communication with each other and transmit signals through induction. Each downhole component comprises electrical characteristics such as impedance, reactance, capacitance and inductance.
U.S. Pat. No. 6,586,932 discloses an antenna design for a downhole nuclear magnetic resonance logging tool. The logging tool is enhanced to shape the resultant RF field generated by the antenna. The enhancement is accomplished by adding additional turns to a portion of the antenna, either circumscribing a ferrite material or locating it on the surface of an at least partially non-conductive material. The additional turns or half turns in combination with the RF field from parallel antenna portions result in a RF field contribution from the coil portions which are not enhanced. Further, the total RF field can be shaped over an earth sample region depending on placement of the enhancing turns. In this way, for example, the total RF field can be generated to achieve an orthogonal alignment with a static field over a larger region of the sample.
U.S. Pat. No. 6,586,939 discloses a transverse induction logging tool having a transmitter and receiver for downhole sampling of formation properties. The tool has a symmetrical spilt-coil transmitter coil and a bucking coil interposed between the spilt transmitter coils to reduce coupling of the transmitter time varying magnetic field into the receiver. The tool provides symmetrical shielding of the coils and grounding at either the transmitter or receiver end only to reduce coupling of induced currents into the received signal.